Question

请有人告诉我，以下结构有什么问题？：

 CASE @CountryID
        WHEN 1 THEN SET @String = REPLACE(@String,'+420','')
        WHEN 2 THEN SET @String = REPLACE(@String,'+421','')    
        WHEN 3 THEN SET @String = REPLACE(@String,'+359','')    
        WHEN 4 THEN SET @String = REPLACE(@String,'+7','')  
        WHEN 5 THEN SET @String = REPLACE(@String,'+48','') 
        WHEN 7 THEN SET @String = REPLACE(@String,'+63','') 
    END

@CountryID是INT。

问题出现在CASE声明构造中，因为IF语句运行良好，但我看不到任何故障，尝试了不同类型的案例构建并搜索文档。

任何提示都会受到赞赏。

Answer 1

您需要使用：

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CASE is expression ，但您将其用作SELECT @String = CASE @CountryID WHEN 1 THEN REPLACE(@String,'+420','') WHEN 2 THEN REPLACE(@String,'+421','') WHEN 3 THEN REPLACE(@String,'+359','') WHEN 4 THEN REPLACE(@String,'+7','') WHEN 5 THEN REPLACE(@String,'+48','') WHEN 7 THEN REPLACE(@String,'+63','') -- ELSE @String -- to avoid NULL if no country found END;（例如在Oracle / DB2中可用）

Oracle支持 CASE statement （在CASE statement中不可用）：

T-SQL

和 CASE expression ：

CASE
    WHEN jobid = 'PU_CLERK' THEN sal_raise := .09;
    WHEN jobid = 'SH_CLERK' THEN sal_raise := .08;
    WHEN jobid = 'ST_CLERK' THEN sal_raise := .07;
    ELSE sal_raise := 0;
  END CASE;

修改

如HABO所述，您可以将其重写为：

appraisal := CASE grade WHEN 'A' THEN 'Excellent' WHEN 'B' THEN 'Very Good' WHEN 'C' THEN 'Good' WHEN 'D' THEN 'Fair' WHEN 'F' THEN 'Poor' ELSE 'No such grade' END;

或者在SQL Server 2012及更高版本中，您可以使用SELECT @String = REPLACE(@String, CASE @CountryID WHEN 1 THEN '+420' WHEN 2 THEN '+421' WHEN 3 THEN '+359' WHEN 4 THEN '+7' WHEN 5 THEN '+48' WHEN 7 THEN '+63' ELSE '' END, '');：

CHOOSE

Answer 2

@ lad2025重写了有效的代码（并且有一个很好的解释！）。我想指出在SQL Server中，我更喜欢：

SELECT @String = REPLACE(@String, v.str, '')
FROM (VALUES (1, '+420'), (2, '+421'), (3, '+359'), (4, '+7'),
             (5, '+48'), (7, '+63')
     ) v(countryId, str)
WHERE v.countryId = @CountryID;

如果没有匹配，我认为这不会改变@String的值。

带参数的CASE语句构造

2 个答案: